滇池沉积物氮内源负荷特征及影响因素

研究了滇池沉积物间隙水氮浓度垂向分布特征,根据Fick扩散定律定量估算了沉积物-水界面氮扩散通量,并探讨了其影响因素.结果表明:滇池沉积物间隙水溶解性总氮(DTN)主要以氨态氮(NH4+-N)形式存在,占其总量的72.30%,其浓度随深度增加而升高;其次为溶解性有机氮(DON),占其总量的24.59%,其浓度随深度的增加先升高后降低,最后趋于稳定;硝态氮(NO3--N)所占比例较低,浓度随深度的增加而降低.滇池沉积物-水界面NH4+-N扩散通量分布范围为12.73~59.74mg/(m2·d)均值30.18mg/(m2·d)],全湖年均氨氮释放量为3305.04t,其中草海、外海北部、东北部及南部湖区扩散通量较大,达35mg/(m2·d),全湖呈由北向南逐渐降低的空间分布特征;全湖年均DON释放量为1147.55t,其全湖分布特征与氨氮一致;NO3--N扩散通量分布范围为-2.70~0.27mg/(m2·d)均值-0.50mg/(m2·d)],总体表现为由上覆水向沉积物扩散.与我国其他湖泊相比,滇池具有较大沉积物氮内负荷,其沉积物-水界面NH4+-N扩散通量较高,对湖泊水体氨氮浓度贡献较大,且其与沉积物总氮、有机质、可交换态氮和可交换态氨氮含量呈显著正相关,即滇池沉积物NH4+-N释放主要受其可交换态氮,特别是可交换态中氨氮含量影响;同时,滇池沉积物DON潜在释放风险也较大,且与沉积物C/N有关.

Characteristics of internal nitrogen loading and influencing factors in Dianchi Lake sediment

The vertical distribution characteristics of the pore water nitrogen concentration of the sediment from Dianchi Lake are studied, the nitrogen diffusion flux at its sediment-water interface was estimated quantitatively based on Fick diffusion law, and its influencing factors were also discussed. The results show: The total dissolved nitrogen of the sediment pore water from Dianchi Lake was mainly in the form of NH4+-N, accounting for 72.30%, With the increasing depth its concentration presented an increasing trend; followed by dissolved organic nitreogen (DON), accounting for 24.59%, with the increasing depth the concentration presented a trend of first increasing then decreasing gradually stabilized. NO3--N accounted for a lower proportion, and the concentration with depth increasing showed a decreasing trend. The amount of the NH4+-N diffused at sediment-water interface was between 12.73 and 59.74mg/m2·d With an average of 30.18mg/(m2 ·d)]. The amount of the NH4+-N released was 3305.04t per year for the whole lake, and those of Caohai, Northern, Northeast and South of Waihai were large, average 35mg/(m2·d). Their spatial distribution presented decreasing trend from the north region to the south region gradually, the amount of the DON released was 1147.55t annual, which had a similar spatial distribution with NH4+-N. The amount of the NO3--N diffusion flux was from -2.70 to 0.27mg/(m2·d) with an average of -0.50mg/(m2·d)], and its releasing trend was from the overlying water to the sediment. Compared with other lakes in our country, the sediment from Dianchi Lake with the larger nitrogen concentration, its NH4+-N fluxes at sediment-water interface was higher, so there was the larger effect on the ammonia concentration of the overlying water. That was significantly positively correlation between its NH4+-N fluxes from the sediment with its total nitrogen, organic matter, exchangeable nitrogen and ammonia nitrogen content of exchangeable in sediment, so the NH4+-N released of the sediment from Dianchi Lake was mainly influenced by its exchangeable nitrogen, particularly ammonia nitrogen content. The potential risk of the DON release from sediment was large, which was correlated with its values of C/N in sediment significantly at the same time.